And that's precisely why 'spikes' or 'POCs' exist. It's way more common to not have all the answers if you are working on anything remotely interesting. There should be some time to explore solutions. In even more interesting cases, solving the unknowns is the entire project.
It seems that the author has never encountered the "research" side of R&D.
Where does the article imply that seniors don’t do research? How exactly do you expect that anyone can know these things without doing research? The point of the article is that juniors jump into the work without doing the research to figure these things out, while seniors take the time to figure these things out. Sure, maybe they can do that quickly based on experience, but I don’t think the article implies that seniors don’t do research.
It seems that the author has never encountered the "research" side of R&D.